Wireless sensor network systems (WSNSs) have been known that distribute and arrange sensor nodes (hereinafter simply called nodes) to sensing targets such as cliffs, loads, and buildings and collect conditions of the sensing targets using wireless communication. An example of the WSNSs includes an observation apparatus that collects conditions detected by respective nodes and determines the condition of the sensing target on the basis of the collecting result.
Each node, however, does not have an amount of power large enough to enable the node to directly communicate with the observation apparatus, i.e., has a limited amount of power for wireless communication. The WSNS, thus, employs multi-hop communication by which the collected condition is relayed between adjacent nodes. As a result, the observation apparatus can collect the conditions collected by the respective nodes using the multi-hop communication between nodes in the WSNS.
Conventional technologies are described in Japanese Laid-open Patent Publication No. 2007-60342, Japanese Laid-open Patent Publication No. 2014-22770, and Japanese Laid-open Patent Publication No. 2011-13765, for example.
To reliably perform the multi-hop communication with the node serving as a communication partner, the amount of transmission power for multi-hop communication of each node is often set to a maximum amount by default. As a result, the power consumption of each node is large. In this way, the amount of transmission power of each node is statistically or equally set.